In the past, the National Aeronautics and Space Administration has conducted short duration tests of space engines and control thrusters using steam-driven ejector systems (at about 10 mm of mercury vacuum), an example of which is disclosed in U.S. Pat. No. 2,939,316 to Beecher et al. These systems have worked well in the past in providing a low pressure environment simulating conditions space engines will encounter in low earth orbit.
At the present time, NASA has a requirement for a test system to perform long duration sea level testing of a whole family of ultra-high expansion ratio space engines operating at simulated space conditions. Most of these engines have a nozzle area ratio (ratio of exit area to throat area) of between 200:1 and 650:1. Ideally, however, such a system should be able to accommodate rocket engines with nozzle area ratios up to 2,000:1. In addition, the system should be able to accommodate the testing of space engines at 10% power levels with chamber pressures as low as 40 PSIA. Run times should be 30 minutes or longer. Testing of modern space engines requires a test environment having a pressure equivalent to three or four millimeters of mercury. As a practical matter, the type of space engines described above cannot readily be tested by steam systems because of cost, time and facility size requirements.
Another prior art patent is U.S. Pat. No. 2,763,155 to Beams et al. This is an early system for simulating high altitude conditions in order to test hydrocarbon/air combustion under such conditions. Beams et al discloses a two-stage ejector system having a first ejector with a large nozzle fed from its large outlet conduit and a second ejector having a small nozzle fed from a branch conduit which connects with the main conduit directly adjacent to the first ejector nozzle. While the Beams et al device may have been useful in the 1950's in early experimental work relating to combustion at high altitudes, it did not contemplate and did not provide a system actually capable of long duration testing of space engines at sea level. It has an ejector arrangement of doubtful efficiency and does not provide a system capable of being upsized or upgraded to test large modern space engines. Moreover, it does not envision or provide a way to adjust flow rate, and it does not provide a complete test system including a space simulation chamber for receiving space engines to be tested.
Therefore, the object of this invention is to develop a system providing a large high vacuum environment for testing space engines of the type mentioned above, such system being reliable and comparatively inexpensive in construction and operation costs.